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Poster D54, Friday, August 17, 4:45 – 6:30 pm, Room 2000AB

Neural plasticity and right hemisphere contributions to recovery of sentence comprehension in aphasia: evidence from sentence processing treatment

Elena Barbieri1, Jennifer E. Mack1, Brianne M. Chiappetta1, Eduardo R.H. Europa1, Cynthia K. Thompson1;1Northwestern University

Many studies have shown evidence of language recovery and associated neural changes in both the ipsilesional (typically left hemisphere (LH)) and contralesional (right hemisphere (RH)) in chronic post-stroke aphasia (see [1] for a review). A prevailing debate, however, concerns the suitability of tissue within the RH versus LH to support recovery. Some suggest that recruitment of undamaged tissue in the LH results in better recovery [2], with that in the RH reflecting maladaptive neural plasticity, associated with poor recovery [3]. Whereas, others have shown that RH recruitment, particularly within regions homologous to LH language networks, is associated with good recovery [4,5]. The present study examine neural plasticity within both the LH and RH following a 3-month language treatment that targeted production and comprehension of passive sentences (Treatment of Underlying Forms [6]). The study included 18 individuals with chronic stroke-induced aphasia, who were randomly assigned to receive treatment (N=13) or to serve as control participants (N=5). Prior to and following the treatment/control period, all participants’ comprehension and production of trained sentences, as well as untrained related and unrelated structures was tested. Participants also performed a block-design sentence-picture verification fMRI task, in which comprehension of active and passive sentences was alternated with blocks of a control condition (scrambled picture presented with reversed speech) and an eyetracking task evaluating on-line processing of active and passive sentences. Results showed significant improvement in comprehension and production of trained passive sentences (p<.001), as well as generalization to untrained related structures (p<.001) in the treatment group, but not in the control group. Patterns of eye movements during processing of passive sentences also showed emergence of an agent-first strategy for the treated, but not the untreated participants. Neuroimaging data showed upregulation within the LH middle frontal gyrus, RH inferior frontal gyrus, and the superior parietal lobule (bilateral) only in the treatment group, whereas both participant groups showed upregulation within the RH anterior supramarginal gyrus. In addition, region-of-interest (ROI) analyses revealed a positive relation (p=.029) between treatment outcomes in comprehension and upregulation in the RH homologue of regions within the sentence processing network [7], but no relation between behavioral gains and activation in regions within a non-linguistic control network (the dorsal attention network). These findings indicate that the RH contributes to the restoration of both offline and on-line processing of complex sentences in chronic aphasia, and provide evidence that RH homologous of language networks, rather than domain-general systems, support recovery [8]. References [1] Hartwigsen, G., & Saur, D. (2017). NeuroImage. [2]. Fridriksson, J., et al. (2012). NeuroImage, 60(2), 854-863. [3]. Heiss, W.D. & Thiel, A. (2006). Brain and Language, 98(1), 118-123. [4]. Kiran, S., et al. (2015). Frontiers in Human Neuroscience, 9. [5]. Thompson, C.K., et al. (2010). Neuropsychologia, 48(11): 3211-3227. [6]. Thompson, C.K., & Shapiro, L.P (2005). Aphasiology, 19(10-11), 1021-1036. [7]. Walenski, M., et al. (submitted). Human Brain Mapping. [8]. Geranmayeh, F., et al. (2014). Brain, 137(10), 2632-2648.

Topic Area: Language Disorders